Multi-Revolution Absolute High-Resolution Rotation Measurement System And Bearing Equipped With Such A System

Abstract

A rotation measurement system comprises a rotatable annular magnetic encoder 16 carrying a series of encoding elements 23 arranged around the circumference of the encoder according to a periodic pattern, characterized in that it comprises a primary sensor assembly 38 comprising at least a primary magnetic sensor 38 disposed facing the encoding elements for detecting the angular position of the encoder with a discrete angular resolution of a fraction of a revolution equal to or less than one period of the encoder and an electronic counter for the number of fractions of a revolution made, and a secondary sensor assembly comprising secondary magnetic sensors 24 a to 24 d, 25 a to 25 d disposed facing the encoding elements for determining an absolute position of the encoder between two positions separated by at least one fraction of a revolution.

1 . Rotation measurement system, comprising:
 a rotatable annular magnetic encoder carrying a series of encoding elements arranged around the circumference of the encoder according to a periodic pattern;   a primary sensor assembly comprising at least a primary magnetic sensor disposed facing the encoding elements for detecting the angular position of the encoder with a discrete angular resolution of a fraction of a revolution equal to or less than one period of the encoder and an electronic counter for the number of fractions of a revolution made; and   a secondary sensor assembly comprising secondary magnetic sensors disposed facing the encoding elements for determining an absolute position of the encoder between two positions separated by at least one fraction of a revolution.   
   
   
       2 . System according to  claim 1 , further comprising main power supply means for the primary and secondary sensor assemblies, and temporary power supply means for the primary sensor assembly such that the said primary sensor assembly is kept operational in case of a main power supply failure. 
   
   
       3 . System according to  claim 2 , wherein the temporary power supply means comprises a capacitor of high capacitance, a battery and/or a cell. 
   
   
       4 . System according to  claim 1 , wherein the periodic pattern is repeated circumferentially at least twice on the encoder. 
   
   
       5 . System according to  claim 1 , wherein the secondary sensor assembly comprises at least two sensors angularly separated by a non-integer number of periods and an interpolator capable of determining an absolute position of the encoder by comparison of the signals from the two sensors. 
   
   
       6 . System according to  claim 5 , wherein the secondary sensor assembly comprises at least a first group of sensors and a second group of sensors, the sensors of one group being situated facing the encoding elements while being angularly separated one relative to another by an integer number of periods, the sensors of one group being angularly separated by a non-integer number of periods relative to the sensors of the group. 
   
   
       7 . System according to  claim 6 , further comprising a second group separated from the first group by a quarter of a period. 
   
   
       8 . System according to  claim 6 , further comprising means for adding together the measurement signals originating from the sensors of one group into a resultant single signal. 
   
   
       9 . System according to  claim 1 , wherein the primary sensor assembly comprises a passive sensor, and preferably at least two passive sensors. 
   
   
       10 . System according to  claim 9 , wherein the primary sensor assembly comprises a reed relay switch and/or a sensor of the Wiegand wire type. 
   
   
       11 . System according to  claim 1 , wherein the resolution of the primary sensor assembly is at most equal to a quarter of a period. 
   
   
       12 . Instrumented bearing comprising an outer ring, an inner ring, at least one row of rolling elements, and a rotation measurement system according to  claim 1 .